The major goal of the Section on Developmental Neurobiology is the elucidation of basic principles governing the development and plasticity of prefrontal granular cortex in primates. The research program is composed of three integral parts: (1) analysis of the development and organization of certain classes of prefrontal cortical connections:; 2) analysis of the functional maturation of the prefrontal cortex and related structures; and (3) assessment of structural and functional plasticity which follows early injury to the prefrontal cortex. The goals of this multifaceted project are achieved by a broad multidisciplinary approach including behavioral, anatomical, electrophysiological and biochemical techniques. These techniques are used in conjunction with recently refined procedures that permit prenatal neurosurgery on the primate brain with return of the fetus to the uterus and survival to and after term. The studies are conducted on the rhesus monkey because the expanse of association cortex in this species as well as its neuronal organization, protracted development and capacity for complex behavior makes it an excellent animal model for the study of normal and pathological development of human neocortex.